Active sliding generated by cross-bridges between filaments is believed to be the basis for movement in flagella and cilia, as well as in muscle. Computer simulation methods have been developed for relating the movement of a flagellum to properties of its movement-generating cross-bridges, and for analysis of the force and chemical turnover rate of cross-bridge populations. Further exploration of cross-bridge models for flagella and muscle is required to fully exploit existing and new experimental data, and new ideas about mechanisms for oscillation in flagella. This work should lead to new insights into cross-bridge function in flagella and cilia, which may be applicable to muscle and other motile systems. Additionally, this work is prerequisite to computer simulation analysis of the function of the outer dense fibers of mammalian spermatozoa, which could form a basis for development of more specific contraceptive agents.